/*
 ** License Applicability. Except to the extent portions of this file are
 ** made subject to an alternative license as permitted in the SGI Free
 ** Software License B, Version 1.1 (the "License"), the contents of this
 ** file are subject only to the provisions of the License. You may not use
 ** this file except in compliance with the License. You may obtain a copy
 ** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
 ** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
 ** 
 ** http://oss.sgi.com/projects/FreeB
 ** 
 ** Note that, as provided in the License, the Software is distributed on an
 ** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
 ** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
 ** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
 ** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
 ** 
 ** Original Code. The Original Code is: OpenGL Sample Implementation,
 ** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
 ** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
 ** Copyright in any portions created by third parties is as indicated
 ** elsewhere herein. All Rights Reserved.
 ** 
 ** Additional Notice Provisions: The application programming interfaces
 ** established by SGI in conjunction with the Original Code are The
 ** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
 ** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
 ** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
 ** Window System(R) (Version 1.3), released October 19, 1998. This software
 ** was created using the OpenGL(R) version 1.2.1 Sample Implementation
 ** published by SGI, but has not been independently verified as being
 ** compliant with the OpenGL(R) version 1.2.1 Specification.
 **
 */
/*
 ** Author: Eric Veach, July 1994.
 **
 ** $Date: 2001/03/17 00:25:41 $ $Revision: 1.1 $
 ** $Header: /home/krh/git/sync/mesa-cvs-repo/Mesa/src/glu/sgi/libtess/tessmono.c,v 1.1 2001/03/17 00:25:41 brianp Exp $
 */

#include "gluos.h"
#include <stdlib.h>
#include "geom.h"
#include "mesh.h"
#include "tessmono.h"
#include <assert.h>

#define AddWinding(eDst,eSrc)	(eDst->winding += eSrc->winding, \
	eDst->Sym->winding += eSrc->Sym->winding)

/* __gl_meshTessellateMonoRegion( face ) tessellates a monotone region
 * (what else would it do??)  The region must consist of a single
 * loop of half-edges (see mesh.h) oriented CCW.  "Monotone" in this
 * case means that any vertical line intersects the interior of the
 * region in a single interval.  
 *
 * Tessellation consists of adding interior edges (actually pairs of
 * half-edges), to split the region into non-overlapping triangles.
 *
 * The basic idea is explained in Preparata and Shamos (which I don''t
 * have handy right now), although their implementation is more
 * complicated than this one.  The are two edge chains, an upper chain
 * and a lower chain.  We process all vertices from both chains in order,
 * from right to left.
 *
 * The algorithm ensures that the following invariant holds after each
 * vertex is processed: the untessellated region consists of two
 * chains, where one chain (say the upper) is a single edge, and
 * the other chain is concave.  The left vertex of the single edge
 * is always to the left of all vertices in the concave chain.
 *
 * Each step consists of adding the rightmost unprocessed vertex to one
 * of the two chains, and forming a fan of triangles from the rightmost
 * of two chain endpoints.  Determining whether we can add each triangle
 * to the fan is a simple orientation test.  By making the fan as large
 * as possible, we restore the invariant (check it yourself).
 */
int __gl_meshTessellateMonoRegion( GLUface *face )
{
	GLUhalfEdge *up, *lo;

	/* All edges are oriented CCW around the boundary of the region.
	 * First, find the half-edge whose origin vertex is rightmost.
	 * Since the sweep goes from left to right, face->anEdge should
	 * be close to the edge we want.
	 */
	up = face->anEdge;
	assert( up->Lnext != up && up->Lnext->Lnext != up );

	for( ; VertLeq( up->Dst, up->Org ); up = up->Lprev )
		;
	for( ; VertLeq( up->Org, up->Dst ); up = up->Lnext )
		;
	lo = up->Lprev;

	while( up->Lnext != lo ) {
		if( VertLeq( up->Dst, lo->Org )) {
			/* up->Dst is on the left.  It is safe to form triangles from lo->Org.
			 * The EdgeGoesLeft test guarantees progress even when some triangles
			 * are CW, given that the upper and lower chains are truly monotone.
			 */
			while( lo->Lnext != up && (EdgeGoesLeft( lo->Lnext )
					|| EdgeSign( lo->Org, lo->Dst, lo->Lnext->Dst ) <= 0 )) {
				GLUhalfEdge *tempHalfEdge= __gl_meshConnect( lo->Lnext, lo );
				if (tempHalfEdge == NULL) return 0;
				lo = tempHalfEdge->Sym;
			}
			lo = lo->Lprev;
		} else {
			/* lo->Org is on the left.  We can make CCW triangles from up->Dst. */
			while( lo->Lnext != up && (EdgeGoesRight( up->Lprev )
					|| EdgeSign( up->Dst, up->Org, up->Lprev->Org ) >= 0 )) {
				GLUhalfEdge *tempHalfEdge= __gl_meshConnect( up, up->Lprev );
				if (tempHalfEdge == NULL) return 0;
				up = tempHalfEdge->Sym;
			}
			up = up->Lnext;
		}
	}

	/* Now lo->Org == up->Dst == the leftmost vertex.  The remaining region
	 * can be tessellated in a fan from this leftmost vertex.
	 */
	assert( lo->Lnext != up );
	while( lo->Lnext->Lnext != up ) {
		GLUhalfEdge *tempHalfEdge= __gl_meshConnect( lo->Lnext, lo );
		if (tempHalfEdge == NULL) return 0;
		lo = tempHalfEdge->Sym;
	}

	return 1;
}


/* __gl_meshTessellateInterior( mesh ) tessellates each region of
 * the mesh which is marked "inside" the polygon.  Each such region
 * must be monotone.
 */
int __gl_meshTessellateInterior( GLUmesh *mesh )
{
	GLUface *f, *next;

	/*LINTED*/
	for( f = mesh->fHead.next; f != &mesh->fHead; f = next ) {
		/* Make sure we don''t try to tessellate the new triangles. */
		next = f->next;
		if( f->inside ) {
			if ( !__gl_meshTessellateMonoRegion( f ) ) return 0;
		}
	}

	return 1;
}


/* __gl_meshDiscardExterior( mesh ) zaps (ie. sets to NULL) all faces
 * which are not marked "inside" the polygon.  Since further mesh operations
 * on NULL faces are not allowed, the main purpose is to clean up the
 * mesh so that exterior loops are not represented in the data structure.
 */
void __gl_meshDiscardExterior( GLUmesh *mesh )
{
	GLUface *f, *next;

	/*LINTED*/
	for( f = mesh->fHead.next; f != &mesh->fHead; f = next ) {
		/* Since f will be destroyed, save its next pointer. */
		next = f->next;
		if( ! f->inside ) {
			__gl_meshZapFace( f );
		}
	}
}

#define MARKED_FOR_DELETION	0x7fffffff

/* __gl_meshSetWindingNumber( mesh, value, keepOnlyBoundary ) resets the
 * winding numbers on all edges so that regions marked "inside" the
 * polygon have a winding number of "value", and regions outside
 * have a winding number of 0.
 *
 * If keepOnlyBoundary is TRUE, it also deletes all edges which do not
 * separate an interior region from an exterior one.
 */
int __gl_meshSetWindingNumber( GLUmesh *mesh, int value,
		GLboolean keepOnlyBoundary )
{
	GLUhalfEdge *e, *eNext;

	for( e = mesh->eHead.next; e != &mesh->eHead; e = eNext ) {
		eNext = e->next;
		if( e->Rface->inside != e->Lface->inside ) {

			/* This is a boundary edge (one side is interior, one is exterior). */
			e->winding = (e->Lface->inside) ? value : -value;
		} else {

			/* Both regions are interior, or both are exterior. */
			if( ! keepOnlyBoundary ) {
				e->winding = 0;
			} else {
				if ( !__gl_meshDelete( e ) ) return 0;
			}
		}
	}
	return 1;
}